Breech mechanism for automatic firearms



Nov. 8, 1949 G. WEBB ETAL BREECH MECHANISM FOR AUTOMATIC FIREARMS FiledNov. 9, 1945 550x55 Webb 22L SWEF'E J'F'zvanbars WIYZIE .M flttarng'nections.

Patented Nov. 8, 1949 BREECH MECHANISM FOR AUTOMATIC FIREARMS GeorgeWebb, Hartford, Conn., and William L.

Swartz, Miami, Fla., assignors to Colts Manufacturing Company, acorporation of Connecticut Application November 9, 1945, Serial N 0.627,627

8 Claims.

The invention relates particularly to a breech mechanism for a firearmof the type wherein the barrel and the breech structure are permitted toreciprocate bodily as a unit during recoil and counter-recoil, thefeeding mechanism in its entirety remaining stationary during suchreciprocation. A firearm of the type referred to is disclosed in thepatents to Marc Birkigt, Nos. 2,159,- 126, 2,159,127, 2,199,871 and2,199,872.

With a firearm of the type referred to, the breech bolt islongitudinally reciprocable in the 'breech casing and there is areleasable locking mechanism for holding the bolt in its forwardbreeched position. For releasing the locking mechanism and for applyingforce to move the bolt rearward, there is provided a push rod, orpreferably two push rods, movable rearwardly upon firing. Heretoforethese push rods have been actuated by a gas operated means receivinggases of explosion from the barrel, the said gases reacting upon apiston which in turn moved the push rods by means of suitable mechanicalcon- The gas operated mechanism has been frequently found objectionableon account of clogging of the gas passages, or on account of sticking ofthe piston with resultant delayed action, or for other reasons.Furthermore, with a gas operated mechanism the rate of rearward movementof the push rods has no fixed or determined relationship to the rate ofrearward recoil movement of the barrel and casing.

The principal object of the present invention is to eliminate the gasoperated mechanism with its inherent objections, and to provide for thesame purpose a simple and positively acting mechanical device, whichwill reliably actuate the release mechanism for the lock and also movethe bolt rearward Whenever recoil movement occurs.

A further object of the invention is to insure movement of the push rodsin definitely timed relationship with the rearward recoil movement ofthe barrel and easing.

A still further object of the invention is to provide a graduallyaccelerated rate of rearward movement of the push rods, such graduallyac celerated movement being in definitely timed relationship with therearward recoil movement of the barrel and easing.

Other objects of the invention will be apparent from the accompanyingdrawing and from the following specification and claims.

Of the drawing:

Fig. 1 is a side view of a firearm embodying the invention, the feedmechanism being omitted and. certain portions of the firearm beingbroken away with other portions shown in section along the line I-l ofFig. 2.

Fig. 2 is a plan view of the firearm shown in Fig. 1 with certainportions shown in section along the line 2--2 of Fig. 1.

Fig. 3 is an enlarged fragmentary view similar to Fig. 1 but showing theparts in different relative positions,

Fig. 4 is a front view of the lock release mechanism to which theinvention particularly relates, the casing being omitted and the barrelbeing shown in dot-and-dash lines.

Fig. 5 is a vertical sectional view taken along the line 5--5 of Fig. 4.

Fig. 6 is a vertical sectional view taken along the line 66 of Fig. 4.

Fig. 7 is a view similar to Fig. 5 but showing an alternativeconstruction.

Referring to the drawing, II and I2 represent respectively the barreland the breech casing of a firearm of the type to which the invention isparticularly applicable. In use, the firearm is so mounted that thebarrel and the breech casing can reciprocate longitudinally as anentirety when firing occurs.

Carried by the casing I2 and in slidable engagement therewith is a slidemember l3 which is adapted to carry a suitable feed mechanism ormagazine, not shown. By means to be described, the slide member I3 isheld stationary notwithstanding reciprocation of the barrel and casing.The feed mechanism is detachably connected with the slide I3, having aportion adapted to be engaged under a hook I4 and having another portionadapted to be engaged by a latch l5 controlled by a lever IB.

Positioned within the casing I2 is a breech bolt I! which islongitudinally reciprocable relatively to the casing. A releasable lockis provided for holding the bolt I! in its forward breeched positionand, as shown, this look includes a strut I8 pivotally engaged at itsforward end with the bolt and seated at its rear end in a notch in atransverse member I9 carried by the casing. Positioned at opposite sidesof the breech bolt I1 and guided for longitudinal movement separatetherefrom are two unlocking plates 20, 2E]. The plates 20, 20 are tiedtogether by a cross member 2| which extends through a slot 22 in thebolt I I, the width of the slot being greater than the width of thecross member. Each plate 20 has a notch 23 having a rearward facing camsurface, and the strut l8 has upward projecting hooks 24 projecting intothe notches 23 and having forward facing cam surfaces adapted to engagewith the rearward cam surfaces of the notches. When the plates are intheir forward positions as shown in Figs. 1 and 2, the rear end of thestrut i8 is seated in the notch in the transverse member l9 and the boltl! is locked in its forward breeched position, The cross member 2| is atthe front of the slot 22. However, when the plates are moved rearwardrelatively to the breech bolt, the before-mentioned cam surfaces engageeah other with the result that the strut 18 is swung upward to theposition Shown in Fig. 3, being thus removed from the notch and beingfree to mpye rearward over the top of the member l9. The bolt I1 is thusunlocked and move rearifiard upon recoil. Rearward movement of theplates 2|], 20 with respect to the bolt I] is limited by engagement ofthe cross member 2! with the rear of the slot 22. Upon counter-recoilthe bolt returns to its forward breeched position and the strut I3returns to the locking position as shown in Fig. 1.

For moving the plates 26, 20 there are provided two push rods 25, 25which are carried by the casing and which are longitudinally movablerelatively thereto. Each push rod abuts at its rear against the front orthe corresponding unlocking plate 20. It will be observed that the pushrods 25, 25 serve not only to eifect unlockii'ig as described, but alsoserve after the plates 20 have reached their limit of rearward relativemovement to apply pressure to the bolt to insure its rapid rearwardmovement in the breech casin l2. The mechanism as thus fardescribedisold in the art and does not of itself constitute any part of the presentinvention. Two separate plates 20, 20 and two separate push rods 25, 25are commonly used and are preferred, but the inventionis not necessarilyso limited. However, the novel mechanism to be now described is adaptedfor use with two push rods; and this is the mechanism preferred.

It has already been stated that the barrel and the breech casing arelongitudinally reciprocable upon firing, and that the slide member [3 isheld stationary notwithstanding the reciprocatory movement of the barreland casing. In accordance with the present invention, the relativemovement of the casing with respect to the slide member upon firing isutilized to move the push rods longitudinally so as to effect therelease of the lock. When two transversely spaced push rods 25, 25 areprovided as is preferred, there are provided two transversely spacedlevers Z6, 26 each having between its ends a pivot aperture forreceiving a transverse pivot pin 21 carri d by the reciprocable casingl2 and each engaging at 28 near its lower end with the correspondingpush rod Each lever 26 has a slot 29 near its u per end for receiving astationary pivot pin 30 carried by or connected with the station iitslide l3. The result is that when the casing l2 moves rearward duringrecoil the pivotal connection at 21 moves rearward, and inasmuch as thepivotal connection at 30 is stationary the levers 26, 23 move in theclockwise direction about the piv} otal axis at 21 and serve to push therods 25, 25 toward the rear to effect unlocking as shown in Fig. 3. Whenthe casing moves forward at; counter-recoil, the levers 25, 28 arerestored to the positions shown in Fig. 1 and the push rods 25, 25 arefree to move forward to the 'ptsitiah 7 shown in that figure.

It Will be seen that in View Of the dsbiibd mechanical actuating meansfor the push rods, the said rods are moved in definite predeterminedtimed relationship with the recoil movement of the barrel and casing.Thus the unlocking and the initial movement of the bolt are effected intimed relation to the recoil movement.

A lug or projection 3l extends upward from the top of the casing at thefront end thereof and a bracket 32 is secured to the forward face ofthis lug, the said bracket carrying the pivot pin 21; Two forwardextending brackets 33, 33 are secured by cap screws 34, 34 to the slide3 at opposite sides thereof, these brackets near their forward endscarrying the transverse pivot pin 30. Preferably; the brackets 33, 33are utilized for maintaining the slide I3 stationary. To this end thebrackets are provided respectively with laterally projecting lugs 35, 33which are engaged by longitudinally extending tie rods 38, 3B, theforward ends of which are secured to a stationary portion of the mountfor the firearm.

In order to hold the pivot pin 30 securely in place and to assist thebrackets 33, 33 in preventing relative upward movement thereof, the saidpin carries a roller 31. A bracket 33 is seciired to the rear face ofthe lug 3| and this bracket has "a portion which extends forward and isimmediately above the roller 37. It will be seen that the bracket 38moveswith the casing and therefore moves relatively to the roller 31,the axis 'of which is stationary. The roller engagiii'g face of thebracket 38 is horizontal and the bracket therefore serves to preventupward movement of the roller .and thus serves to more securely held thepivot pin 30.

Preferably and as shown, the bracket 32 carries a threaded stud '39which projects rearward through a central opening in the lug 3i and intoan opening in the lower rear portion of the bracket 38. Keys 40 preventthe bracket 32 from turning about the axis of the stud. A nut t] engagesthe rear portion of the stud and alsti the bracket 38, the'stud and nutthus servra to hold mpia e both of the brackets 32 and 3B. The bracket32 is shown as having an integrai flange 42 which extends along one sideof the lifg 3|, and is provided With a hole 43. This bracket has nofunction for the o eration of the rods, but serves to carry a member,not shown,,for ope'ratihg the feed mechanism.

In Fig. 7 there is shown an alternative constructioii wherein levers Mare substituted for the ivers 26. Each lever in has a bearing aperturefor receiving the pivot pin 30 and has a longitudinal slot for receivingthe pivot pin 21. It will be seen that whenthe lever 44 moves from theposition shown in Fig. 7, toa position corresponding to that shown inFig. 3, there is a gradual reduction of the length of the lever armrepresented by the distance between the pivot pins 30 and 21 and agradual increase of the length of the lever arm representedby thedistance between the pivot pin 2'! and the point of engagement at 23with the push rod. This gradual change in the relationship between thelengths of the two lever arms causes a gradual acceleration of the rateof movement of the push T65. relative to the rate of movement or thebarrel and easing. V V a Preferably each slot 45, while generallylongitiidi nal; is at man-git to a line connecting the of thepin 21 theaxis of the pin 30 is initially in the lower end of the S1017,

all as shown in Fig. 7, the upper part of the said slot being forward ofthe said line.

It will be seen that the inclined position of the slot 45 with theresultant forward position of the upper end thereof causes increasedrearward movement of the lower end of the lever at 28 with correspondingincreased rearward movement and increased acceleration of thecorresponding push rod 25.

What is claimed is:

1. An automatic firearm comprising in combination, a breech casing and abarrel longitudinally reciprocable upon firing, a slide member havingslidable engagement with the casing, means for holding the slide memberstationary notwithstanding reciprocation of the casing and barrel, abreech bolt in the casing and longitudinally reciprocable relativelythereto, a releas able lock for holding the bolt in its forward breechedposition, means for releasing the lock including a push rod carried bythe casing and longitudinally movable relatively thereto, a lever havingbetween its ends a pivotal connection with the reciprocable casing andengaging near its lower end with the push rod, and means connected withthe stationary slide member and having pivotal connection with the levernear its upper end whereby upon recoil movement of the casing the leveris moved about its first said pivotal connection to move the push rodand thereby release the lock.

2. An automatic firearm comprising in combination a breech casing and abarrel longitudinally reciprocable upon firing, a slide member havingslidable engagement with the casing, means for holding the slide memberstationary notwithstanding reciprocation of the casing and barrel, abreech bolt in the casing and longitudinally reciprocable relativelythereto, a releasable lock for holding the bolt in its forward breechedposition, means for releasing the lock including a push rod carried bythe casing and longitudinally movable relatively thereto, a lever havingbetween its ends a pivotal connection with the reciprocable casing andengaging near its lower end with the push rod, and means connected withthe stationary slide member and having pivotal connection with the levernear its upper end whereby upon recoil movement of the casing the leveris moved about its first said pivotal connection to move the push rodand thereby release the lock, one of said pivotal connections to thelever being slidable upon recoil of the casing to increase as the casingrecoils upon firing the ratio of the distance between said pivotalconnection to the stationary slide member and the push rod engagingportion to the distance between said pivotal connection to thestationary slide member and the pivotal connection with the reciprocablecasing.

3. An automatic firearm comprising in combination, a breech casing and abarrel longitudinally reciprocable upon firing, a slide member havingslidable engagement with the casing, means for holding the slide memberstationary notwithstanding reciprocation of the casing and barrel, abreech bolt in the casing and longitudinally reciprocable relativelythereto, a releasable lock for holding the bolt in its forward breechedposition, means for releasing the lock and for moving the breech boltrearwardly, such means including a push rod carried by the casing andlongitudinally movable relatively thereto, a lever having between itsends a fixed pivotal connection with the reciprocable casing andengaging near its lower end with the push rod, the said lever having alongitudinal slot in its upper end portion, and a stationary pivot pinconnected with the stationary slide member and entering the said slot inthe lever whereby upon recoil movement of the casing the lever is movedabout its said pivotal connection to move the push rod and therebyrelease the lock.

4. An automatic firearm comprising in combination, a breech casing and abarrel longitudinally reciprocable upon firing, a slide member havingslidable engagement with the casing, means for holding the slide memberstationary notwithstanding reciprocation of the casing and barrel, abreech bolt in the casing and longitudinally reciprocable relativelythereto, a releasable lock for holding the bolt in its forward breechedposition, means for releasing the lock 7 and for moving the breech boltrearwardly, such means including a push rod carried by the casing andlongitudinally movable relatively thereto, a lever having a pivotaperture near its upper end and having a generally longitudinal slotbetween its ends and the said lever engaging near its lower end with thepush rod, a pivot pin carried by the reciprocable casing and enteringthe slot in the lever, and a stationary pivot pin carried by thestationary slide member and entering the pivot aperture in the leverwhereby upon recoil movement or" the casing the lever is moved about themovable pivotal connection formed by the first pivot pin and the slot tomove the push rod at a rate gradually accelerated with respect to therate of movement of the casing and barrel.

5. An automatic firearm comprising in combination, a breech casing and abarrel longitudinally reciprocable upon firing, a slide member havingslidable engagement with the casing, means for holding the slide memberstationary notwithstanding reciprocation of the casing and barrel, abreech bolt in the casing and longitudinally reciprocable relativelythereto, a releasable lock for holding the bolt in its forward breechedposition, means for releasing the lock and for moving the breech boltrearwardly, such means including a push rod carried by the casing andlongitudinally movable relatively thereto, a lever having a pivotaperture near its upper end and having a generally longitudinal slotbetween its ends and the said lever engaging near its lower end with thepush rod, the said slot being inclined forwardly from a line extendingthrough the pivot aperture and the lower end of the slot, a pivot pincarried by the reciprocable casing and entering the slot in the lever,and a stationary pivot pin carried by the stationary slide member andentering the pivot aperture in the lever whereby upon recoil movement ofthe casing the lever is moved about the movable pivotal connectionformed by the first pivot pin and the slot to move the push rod at arate gradually accelerated with respect to the rate of movement of thecasing and barrel.

6. An automatic firearm comprising in combination, a breach casing and abarrel longitudinally reciprocable upon firing, a slide member havingslidable engagement with the casing, means for holding the slide memberstationary notwithstanding reciprocation of the casing and barrel, abreech bolt in the casing and longitudinally reciprocable relativelythereto, a releasable lock for holding the bolt in its forward breechedposition, means for releasing the lock including two transversely spacedpush rods carried by the casing and longitudinally movable relativelythereto, a projection on the reciprocable casing carrying a transversepivot pin, two brack levers each having between its ends a pivotaperture receiving the first said pivot pin and each having in its upperend portion a slot receiving the second said pivot pin,- the said leversengaging near their lower ends with the respective push rods whereby thepush rods are moved to release the lock upon recoil movement of thecasing with resultant movement of the levers about the first said pivotpin.

'7. An automatic firearm comprising in combination, a breech casing anda barrel longitudinally reciprocable upon firing, a slide member havingslidable engagement with s the casing, transversely spaced forwardextending brackets on the slide, means engaging the brackets for holdingthe slide member stationary notwithstanding reciprocation of the casingand barrel, a breech bolt in the casing and longitudinally reciprocablerelatively thereto, a releasable lock for holding the bolt in itsforward breeched position, means for releasing the lock including twotransversely spaced push rods carried by the easing and longitudinallmovable relatively thereto, a projection on the reciprocable casingcarrying a transverse pivot pin, a transverse pivot pin above the firstsaid pivot pin andcarried by the said brackets, and two transverselyspaced levers each havin between its endsa pivot aperture receiving thefirst said pivot pin and each having in its upper end portion a slotreceiving the second said pivot pin, the said levers engaging near theirlower ends with the respective push rods whereby the push rods are movedto release the look upon recoil movement of the casing with resultantmovement of the levers about the first said pivot pin.

8. An automatic firearm comprising in combi- 8 nation, a breech casingand a barrel longitudin'ally reciprocable 'upon firing, a slide memberhaving slidable engagement with the casing, means, for holding the saidmember stationary notwithstanding reciprocation of the casing andbarrel, a breech bolt in the casing and longitudinally reciprocablerelatively thereto, a releasable lock for holding the bolt in itsforward breeched position, means for releasing the lock including twotransversely spaced push rods carried by the casing and longitudinallymovable relatively thereto, a projection on the reciprocable casingcarrying a transverse pivot pin, two brackets connected with thestationary slide member and carrying a transverse pivot pin above thefirst said pivot pin, two transversely spaced levers each having betweenits ends a pivot aperture receiving the first said pivot pin and eachhaving in its upper end portion a slot receiving the second said pivotpin, the said levers engaging near their lower ends with the respectivepush rods whereby the push rods are moved to release the lock uponrecoil movement of the cas ing with resultant movement of the leversabout the first said pivot pin, a roller on the second said pivot pin,and a guide carried by the casing and positioned above the roller toengage it and prevent upward movement of the second said pivot pin.

GEORGE WEBB. WILLIAM L. SWARTZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,637,? Von Kiraly et a1. Aug. 2,1927 r 2,159,127 Birkigt May 23; 1939

